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Water Treatment Safe, Clean and Drinkable Assignment • You need to draw and label each step of the water treatment process • Under each label explain what is happening in that step. Water Treatment • Since water is odorless, tasteless, and colorless we must test for specific contaminants such as bacteria, nitrates, arsenic and others. • Natural supplies of potable water are very limited and do not exist in sufficient quantities to meet human needs. • Humans have developed steps to treat the water so it can be used for a specific purpose such as drinking. Water Collection • Water is generally pumped from a lake or river to a treatment facility Screening Most surface water intake facilities are equipped with some type of screening device to prevent large rocks, sticks, and other debris from entering the treatment system. • Large bar racks with openings of 1 and 3 inches apart are commonly used for this purpose. – They are designed specifically to prevent large materials that could damage the intake structure or downstream equipment from entering the treatment system. Screening • Bar racks are usually designed for manual cleaning. • When the raw water source is a river and a bar rack is used, the rack is usually oriented to take advantage of the hydraulics of the river to keep the rack cleaned. • Although trash racks have little effect on turbidity, they do serve an important function in keeping large solids out of the treatment system Coagulation • The addition of alum, lime and other chemicals are added to the water causing particulates to clump together Flocculation • The water is then shaken to form larger clumps which are known as flocs. Sedimentation • The water stands for approximately 24 hours, in which time the clumps settle to the bottom. Filtration • The water passes through filters, some made of layers of sand, gravel, and charcoal that help remove even smaller particles. Disinfection • A small amount of chlorine is added or some other disinfection method is used to kill any bacteria or micro-organisims that may be in the water. • At this stage the water is aerated Storage • Water is placed in a closed tank or reservoir in order for disinfection to take place. The water then flows through pipes to homes and businesses in the community. Clean Water • Substance removed during the treatment process include: – Suspended Solids – Bacteria – Algae – Viruses – Fungi – Minerals – Chemical Pollutants Virtual Water Treatment • http://www.epa.gov/ogwdw/watertreatment plant/flash/index.html Saltwater to Freshwater • How much water on Earth is Saltwater • Can we make it into freshwater • Is it cost effective Assignment • You need to create a flow chart explaining each step in the desalination process • On the bottom explain why people do not use this process more Desalination • Any of several processes that remove some amount of salt and other minerals from saline water. • Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. One potential byproduct of desalination is salt. • Desalination is used on many seagoing ships and submarines. Desalination • One of the most expensive sources of fresh water. • The water sells—depending on site conditions—for between $1,000 and $2,500 per acre-foot (the amount used by two fiveperson U.S. households per year) • Largest plant in nation in San Diego, Ca